1. Field of the Invention
The present invention relates to a wiper device for vehicles, and more particularly, to a wiper device having a lock back function.
2. Description of the Related Art
In general, a rear wiper sometimes needs to be installed on a rear glass of a vehicle according to an inclined angle of the rear glass. A rear wiper is not generally provided on a rear glass of a vehicle of a notch-back style that is called a sedan, but on a hatch-back style vehicle such as a sports utility vehicle (SUV) that essentially has a rear wiper on a rear glass thereof, because that dust is likely to get stuck on the rear glass due to low pressure on the rear glass during driving.
An example of a vehicle having a conventional rear wiper on a rear glass thereof is shown in FIG. 1. In general, a rear wiper consists of a plurality of components. Such a wiper device is disclosed in Korean patent No. 0800581.
Referring to FIG. 1, a conventional wiper device 1 includes three components. That is, the conventional wiper device 1 includes an arm head 2, a retainer 3, and a blade (not shown). The arm head 2 is fixed to a pivot shaft 6 installed on a car body and is rotated together with the pivot shaft 6 by the rotation of the pivot shaft 6. The retainer 3 is coupled to one end of the arm head 2 and transmits the torque of the arm head 2 to the blade. The blade wipes a glass of a vehicle to remove a foreign material on the glass while contacting and sliding on the glass.
In the wiper device 1 having such a structure, generally, a tension spring 5 is used in a connection structure between the retainer 3 and the arm head 2 so that the blade may apply pressure to the glass of the vehicle. One end of the tension spring 5 is hanged to the retainer 3, and the other end of the tension spring 5 is hanged to the arm head 2. Thus, when rotating the retainer 3 in a direction away from the glass of the vehicle due to an action of the tension spring 5, a direction in which the restitutive force of the tension spring 5 acts is changed according to a range of a rotation angle of the retainer 3. That is, an action line TL illustrated in FIG. 1 occurs. A function in which the action direction of the restitutive force of the tension spring 5 is changed is referred to as a toggle action. When the retainer 3 rotates beyond a transversal line, namely, the action line TL due to the toggle action, a lock back state, that is, a state where the blade does not press on the glass of the vehicle and is spaced apart from the glass, occurs. The lock back state is used when exchanging or repairing the blade. However, since recently, a plastic is used as a material of the retainer 3, when a toggle action is repeated between a location of a lock back state and a location of a non-lock back state, a contact portion between the retainer 3 and the arm head 2 is worn, and thus a function of the retainer 3 deteriorates. In addition, when the vehicle repeatedly enters an automatic car wash to be cleaned, the retainer formed of a plastic material is damaged. In particular, a wiper device disclosed in Korean patent No. 0800581 is configured so that a lock back state is attained in two stages, but in this case, a first lock back function may be damaged due to a repeated load.